Pacific Reef Heron Egretta sacra 岩鷺
Category I. Resident in much of HK at low densities, mainly in hard shore areas but also occurs on soft shores.
IDENTIFICATION
Apr. 2016, Michelle and Peter Wong. Adult.
Medium-sized egret, adults are rather uniform slaty-grey at a distance, with dull yellowish legs (though more greyish ‘thighs’), paler tip to bill and yellow irides. At closer range it can be seen the underparts are darker and more uniform than the paler upperparts, the feathers of which are darker around the fringe. Legs are relatively thick and short, only just projecting beyond tail in flight.
Dec 2006, Matthew Kwan. First-winter.
This presumed first-winter bird has dull dark brown wing coverts with slightly paler fringes and brownish feathers remaining on the neck.
Although there are records of grey and white birds, there are none of purely white-phase birds that are considered adequately substantiated. These would be separated from other white egrets in HK by the combination of size, short-legged structure, a thick, variably coloured bill and a broad area of loral skin that has a straight upper edge.
VOCALISATIONS
Generally silent. In flight or when chasing others of its species utters a nasal ‘kyaar’ that is reminiscent of Little Egret but softer.
DISTRIBUTION & HABITAT PREFERENCE
Pacific Reef Herons are found along rocky coastlines mainly in southern and eastern areas of HK. Strongholds are outlying islands such as the Sokos, Po Toi, Waglan, Bluff Island, Tung Lung Chau and the Ninepins, as well as coastal sites at Cape D’Aguilar, Sai Kung, northeast New Territories and on Lamma.
The percentage of 1 km squares in which Pacific Reef Heron was recorded declined from 6.3% in the 1993-96 breeding atlas to 4.9% during the 2016-19 survey. Declines appear to have occurred at Tung Chung/Chek Lap Kok, southwest Lantau, Ma Wan, Cheung Chau and on HK Island, where it appears to be fairly localised. With the exception of north Lantau where extensive development along the coast has resulted in a real decrease, it may be possible that some of these declines are more apparent than real given that Pacific Reef Heron occurs at low densities.
In contrast, there was an increase in the non-breeding season distribution, from 5.4% of surveyed 1 km squares in the 2001-05 winter atlas to 6.4% in the 2016-19 survey. A small increase such as this could be due to better access to difficult to reach coastal areas (e.g., northeast New Territories) or simply stochastic factors (a wider distribution on Lamma in the later survey is different from the more restricted distribution noted there in the second of the breeding atlas surveys).
Pacific Reef Egrets were reported flying over Victoria Harbour or feeding by ferry piers in the 1960s and 1970s. However, there were no subsequent records in the 1980s and 1990s, perhaps due to disturbance from increased shipping traffic and reclamation projects. Although reported from West Kowloon and Tai Koo Shing during the 2016-19 winter atlas, it is now very rare in the inner parts of Victoria Harbour. Increased human disturbance in urban edge areas is presumably a factor in this decline.
Although typically associated with rocky coasts or the boulder edges of reclaimed land, birds often forage in intertidal mudflats close to rockier habitats. They are, however, invariably close to the coast.
OCCURRENCE
Vaughan and Jones (1913) and La Touche (1931-1934) considered Pacific Reef Heron to be an uncommon migrant to this part of China in spring and early summer, while Herklots (1941) recorded the species commonly from December to June. Macfarlane and Macdonald (1966) considered it to be a breeding resident. There is no evidence of anything other than local movements between foraging and roost sites at present. The same pattern is evident today.
The highest single-site count is of 18 birds at Sok Kwu Wan, Lamma on 21 January 2003. There are a number of records of grey (‘pied’) phase individuals from sites throughout HK. Previous records of white-phase birds are now considered not proven.
BREEDING
There are few records of Pacific Reef Egret nesting, but this may be due to the inaccessibility of their preferred breeding sites. A nesting pair was present on Tung Lung Chau from 1957 to 1959, and an abandoned nest was found on Waglan Island in 1959. A nest was found on Kau Yi Chau in 1976 (the species bred there again in 1995), and at Cape D’Aguilar three juveniles were recorded begging for food on 17 June 1995. It seems certain that breeding is more widespread than this suggests.
BEHAVIOUR, FORAGING & DIET
Usually forages solitarily, walking along rocky and muddy shores and the edges of streams flowing into bays taking crabs and fish from the waterline or wet mud. Individuals may also employ ‘flap-feeding’, where food is picked up from the surface of the water in flight, and they may feed from man-made structures and habitats such as breakwaters, light buoys, salt pans, drained ponds and the floating rafts of fish farms. The latter may attract flocks, such as more than 12 at Chi Ma Wan, Lantau on 15 October 1994 and 15 at Long Harbour on 29 December 1994.
Pacific Reef Herons may form small communal roosts, and the highest count is of nine birds flying towards the base of a rocky headland near Ocean Park, Aberdeen. They have also been recorded joining white egrets at roost sites where these are close to the coast such as Penfold Park and Stonecutters, where, during 1996-98, up to three Pacific Reef Egrets roosted in a mixed breeding colony of ardeids on a wooded hillside.
RANGE & SYSTEMATICS
Occupies coastal areas from Bangladesh east to the Korean peninsula and Japan (excluding Hokkaido) and south throughout Asia to Australia and New Zealand and east to Pacific Islands (Martínez-Vilalta et al. 2020). In China it occurs in all coastal areas as far north as the Yangtze (Liu and Chen 2020). The nominate form occurs in the majority of its range including HK. One other subspecies is recognised.
CONSERVATION STATUS
IUCN: Least Concern. Population stable.
Herklots, G. A. C. (1941). The birds of Hong Kong. Part XXXVI. Family Ardeidae (The herons, egrets and bitterns). Hong Kong Naturalist 10: 137-147.
La Touche, J. D. D. (1931-34). Handbook of the birds of Eastern China Vol. 2. Taylor and Francis, London.
Liu, Y. and Y. H. Chen (eds) (2020). The CNG Field Guide to the Birds of China (in Chinese). Hunan Science and Technology Publication House.
Macfarlane, A. M. and Macdonald, A. D., revised by Caunter, J. R. L. and Macfarlane, A. M. (1966). An Annotated Check-list of the Birds of Hong Kong. Hong Kong Bird Watching Society, Hong Kong.
Martínez-Vilalta, A., A. Motis, and G. M. Kirwan (2020). Pacific Reef-Heron (Egretta sacra), version 1.0. In Birds of the World (J. del Hoyo, A. Elliott, J. Sargatal, D. A. Christie, and E. de Juana, Editors). Cornell Lab of Ornithology, Ithaca, NY, USA. https://doi.org/10.2173/bow.pacreh1.01
Vaughan, R. E. and Jones, K. H. (1913). The birds of Hong Kong, Macao and the West River or Si Kiang in South-East China, with special reference to their nidification and seasonal movements. Ibis 1913: 17-76, 163-201, 351-384.
